10 Health and Fitness Calculators That Will Change Your Life

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As we start to see more companies moving towards personal fitness trackers and wearable tech, do we really still have a need for fitness calculators?

The truth is that apps and personal fitness trackers are great for telling you what you’ve already done, but what about when you have a goal in mind and want to know how long it will take you to achieve that goal?

It could be wanting to know how much weight you can lift in an exercise when switching to a different rep range, or how much water you should be drinking during a marathon.

Unfortunately despite some impressive advancements in the technology, it looks like we’re still some way off from having an ‘all-in-one solution’.

This is why we’ve put together the following list of the top 10 fitness calculators we use on a regular basis. Each one has been chosen to assist with a specific problem, and to help you improve every aspect of your physical health.

1. Calories burned calculator

Managing your weight isn’t an easy thing to do. A change in routine but maintaining the same caloric intake can suddenly lead to quite rapid weight change due to one simple reason. Calorie expenditure.

If you’ve changed your job from being very active to being almost completely sedentary, even if you are still taking in the same number of calories, you aren’t going to be burning off the same. This then leads to a surplus, which in turn leads to a short period of sustained weight gain as your body adjusts.

So how do you know how many calories you need to lose or add to your diet in order to maintain your weight?

Similarly, if you’re looking to lose weight and are already on a low calorie diet, how do you know how much exercise you need to do to lose your desired weight in the most natural amount of time?

You need to calculate how many calories you burn each day, and compare this with the number you are taking in.

While you can use our food calorie calculator (number 7 in our list) to determine how many calories you are eating based on your current nutrition plan, you need to perform a completely different calculation to determine the number of calories burned.

For this we will need a calculator.

Difficulties with accurate predictions:

If you’re using indoor fitness equipment as a source of exercise, you might notice that many designs now offer a feedback called ‘Calories Burned’.

In fact, you’ll tend to see this on exercise bikes ranging from $100 up to $5000. So what’s the difference? Surely they are both accurate or they wouldn’t be used as feedback on the display?

Unfortunately this isn’t the case. Many companies will include this as a piece of feedback on their monitors, even though it has undergone no accuracy testing.

The main difference and feature that you need to look for if you want more accurate feedback is the ability to enter your bodyweight into the console.

Even if your exercise bike or personal fitness tracker does give you the option to enter your bodyweight, it can also be useful to cross check against a calculator online.

Our favourite calorie calculator:

In searching for a good calculator for determining the number of calories burned by a particular task or form of exercise, we found that most were very limited in their options.

Even some of the most respected sites could only offer a handful of exercises.

We did however find one site that had a database of activities that was large enough to match most of your daily tasks and exercise routines to.

This is the Calories Burned Calculator from HealthStatus, and it has a wide variety of exercises to choose from, including aerobics, Zumba, running at various speeds, and Bikram Yoga.

You can also choose to include a variety of household tasks, including gardening, chopping wood, and brushing your teeth.

How to use the HealthStatus Calories Burned Calculator:

After using this calculator a few times and searching through many others available online, this is still our favourite due to its wide variety of tasks, and ability to display a single view of your calories burned for the day.

However there is one small improvement we would like to see made. While the final screen does show the exercise next to the number of calories burned, it doesn’t show the duration.

Although this might be easy to remember for one or two tasks, if you’re entering information for a full day it can be nice to know the duration that it corresponds to.

2. Rep calculators

Although rep calculators are usually associated with powerlifters and wanting to estimate their one rep max, they can actually be useful for anyone that trains with weights, regardless of your long term goal.

For example, if you are thinking about changing your routine from high reps to low reps as a way of keeping your routine fresh and effective, you might want to know your 3 or 4 rep max.

It’s worth mentioning that any rep calculator won’t be 100% accurate. That is to say, if your one rep max is calculated at 300 lbs, it may be the case that you can actually only lift 290 lbs, or even 310 lbs.

They are meant as a close estimation as a target you should be aiming towards, which is often enough to help you plan the weight you lift during your warm up sets as well.

While some people believe that your one rep max calculation needs to take into account the exercise, we haven’t seen any accuracy benefit ourselves.

This type of calculator can also be useful for preventing injury. It may be the case that you never want to go as low as a one rep max due to the stress it can put on your CNS if you spend too many consecutive workouts training this way.

Our favourite one rep max calculator:

Although there is also a similar tool available through Bodybuilding.com, our current preference is for the calculator available through ExRx.net.

Like Bodybuilding.com, this allows you to calculate your one rep max based on a particular weight and rep range, as well as a number of useful percentages of that one rep max.

This can then be cross referenced against a chart to determine how many reps you can perform with a given weight, which is usually between 1 and 15.

While Bodybuilding.com focuses purely on Brzycki’s formula, ExRx.net also includes estimations from Baechle and dos Remedios.

Despite there being only minor differences between the three formulas, you might find one to be more accurate for your specific strength levels, and choose to stick with that method in your future calculations.

How to use the ExRx rep calculator:

You can now use the chart below to select your target rep range, choose which formula you want to follow, and match the relevant percentage to the figure in the cell above that relates to this percentage.

For example, imagine if you had just bench pressed 300 lbs for 10 reps. You’re now changing your workout routine so that you only want 6 reps from your strongest set.

In this case you would enter 300 in the ‘Weight Lifted’, 10 for ‘Reps Performed’, then hit Calculate.

If you were following Brzycki’s formula, you would then look at the percentage that matched our target rep range of 6, which would be 83%.

Looking at our percentages above, the closest is 85%, which means you would plan to lift 340 lbs for 6 reps to avoid any loss in strength when you changed your routine.

3. BMI (Body Mass Index) Calculator

Your BMI is a popular unit of measurement used by health professionals to classify your current bodyweight into one of 4 categories; underweight, normal weight, overweight, and obese.

We’ve included this calculator in our list as it can be a useful measurement for many people, but recognise that there are a few cases where this would not be entirely accurate.

The most obvious is when you are carrying a large amount of muscle on your frame, in the event that you are a bodybuilder, powerlifter, or take part in regular resistance workouts.

In this case, you may register a higher BMI reading due to the weight of muscle being disproportionate to your height in the BMI scale.

But for most, it acts as a useful indication of when your bodyweight falls outside of the ideal range, into an area that may be at higher risk of health problems.

Our favourite BMI calculator:

Although we like how easy it is to enter your information in the National Heart Foundation tool, our current favourite has to be the BMI Healthy Weight Calculator from the NHS.

Despite not having the same sliding scales for height and weight, it’s still extremely quick and easy to enter a few basic pieces of personal information. It also takes into account variations in adults and children.

After you enter your gender, age, height, and weight, you can also select an option that best describes your personal activity level.

As soon as you click ‘Next’, you have a large amount of information displayed relating to your BMI, but in a way that’s clear and easy to understand.

You can see your BMI, the different ranges based on your details, your recommended daily caloric intake, and even help and advice on what you can do to bring your result into a healthy range if it’s not already.

If you run a fitness website yourself, they even provide you with an embed code so that you can give visitors to your site easy access to this tool.

4. Hydration calculator

The main goal behind using a hydration calculator is to determine your recommended water intake level for the day.

There have been numerous studies into the importance of water for maintaining a healthy lifestyle, as well as in getting the best performance from your workouts.

But similar to the amount of calories you need to consume each day, the amount of water you should drink depends on a number of physical and environmental factors.

These include gender, exercise environment, exercise intensity, and bodyweight.

Without sufficient water intake you can quickly dehydrate, particularly if you are taking part in sports or cardiovascular exercise on a hot day.

As a result of dehydration, you may then start to suffer muscle cramping and fatigue, which is not just detrimental to the success of that specific workout, but also to your overall health.

The University of Michigan recently put together a document that recommended the following in respect to exercise hydration:

But in terms of specific requirements, it’s difficult to say without knowing some more about the factors we listed above, which can have a big influence on your required water intake.

In fact, even a report produced by the Institute of Medicine into dietary reference intakes concluded with general recommendations of 2.7 litres (91 ounces) per day for women, and 3.7 litres (125 ounces) for men.

They also said that 20 percent of this water intake is expected to come from food, with the remaining 80 percent to be from beverages.

Our favourite hydration calculator:

For general day-to-day water intake calculations, we tend to subscribe to the same recommendations as the Institute of Medicine.

However, there is also a daily water calculator from Bodybuilding.com that calculates your recommended amount based purely on bodyweight, which might be better for younger adults and children.

While this is the recommendation for day-to-day water intake, there are certain exceptions that should also be taken into account.

Marathons for example are one of the most strenuous events that you can put your body through in terms of water loss through sweat.

In this case, studies recommend that you follow a different set of rules entirely – one laid out in the IMMDA Advisory statement by the Professor of Exercise and Sports Science at the University of Cape Town, South Africa.

The main conclusion that this came to was that elite athletes can manage with 200 – 800 ml per hour of running, but no more than 400 – 800 ml per hour. This is to reduce the risk of hyponatremia.

For training specific water intake, we recommend the tool from CamelBak, as we found this to provide the most user friendly interface with explanations for each step.

The questions it asks are also fairly comprehensive, and calculates whether your current intake is enough for your age and body type, or whether it thinks you need to make any changes.

5. Blood pressure health risk calculator

Before you can use this particular calculator, you need to find out your current blood pressure.

In many cases this is something that you can perform on your own at home, which may even be recommended by your doctor if it’s something you need to monitor on a regular basis.

You should also try to keep the influencing factors the same each time you perform this test.

This includes the room temperature, time since you last exercised, time since you last drank caffeine, and time since you last took any medication.

By keeping this the same each week, you’re likely to see less variations, and you will be able to build up a more accurate series of measurements as a result.

How to check your blood pressure at home:

To save repeating some excellent information that’s already available, we would recommend taking a look at the WebMD guide to checking your blood pressure at home.

Our recommended blood pressure health risk calculator:

Although it’s quite a lengthy process to go through, it’s also the most thorough tool we could find.

This is the tool from the American Heart Association that asks you a number of questions based around your physical features and current health conditions, as well as your systolic and diastolic blood pressure readings.

The highest of these two readings (as a percentage of maximum) will then determine your blood pressure category, which is what the calculator will use to base any health advice on.

If your category is high or very high, you are advised to make lifestyle changes, with the next step being used to calculate the likelihood of you making any of these changes.

Based on your ability to follow these lifestyle recommendations, you will then see your risk category adjust to a level that takes these changes into account.

A summary will then be displayed that details your heart attack risk, stroke risk, risk of heart failure, and likelihood of developing kidney disease.

6. Calorie calculator

Whether you’re looking to lose weight, gain it, or simply maintain it, knowing your caloric intake is usually what you will need to be basing your daily food choices upon.

But at the same time, not all calories are equal, with 1g of fat containing 9 calories, and carbs and protein each containing 4 calories per gram.

Most online calculators will provide you with the figure that’s needed to maintain your current weight. This can be influenced by a number of factors including age, height, weight, and gender.

If you’re looking to lose weight, it’s generally recommended that you will need to either eat 500 calories less than this recommended amount each day, or perform exercise that burns the equivalent of 500 calories.

The opposite is true if you are looking to gain weight, where you should aim for 500 calories more than your recommended daily amount each day. (The 500 calorie measurement is based on a safe gain or loss pace of around 1 lb per week)

But unfortunately it’s not quite that simple. You also have to take into account your level of calorie expenditure as a result of physical activity throughout the day.

One of the most reliable research sources you can follow when working out this number is the Harris Benedict Equation and Dietary Reference Intakes, compiled by the Institute of Medicine in 2005.

Our favourite daily calorie calculator:

While there are certainly a large number of daily calorie calculators now available online, our personal favourite is still the one maintained by the Mayo Clinic.

How to use the Mayo Clinic calorie calculator:

7. Food calorie calculator

So you now know how many calories you need to be taking in each day in order to achieve your diet goal, but how do you know how many calories each piece of food has?

It’s not just food either. Knowing how many calories are in certain drinks can have a huge impact on how successful your diet plan is.

Our favourite food calorie calculator:

We’re going to have to cheat a little here and actually say we have 2 favourites; one because of its comprehensive database of foods and drinks, and one because of its ease of use and some really useful added features.

Due to the sheer number of foods and drinks they have in their database, we have to say that our current favourite site for calculating what’s in your food and drink is MyFitnessPal.

Not only do they include everything you would expect to buy on your weekly shop, but they also have information for food from specific fast food restaurants.

So if you ever wanted to find out how much protein was in a Cheeseburger from McDonalds, this is where you would be able to find that information.

The entire database of 4 million+ items is driven by a community of members, which you can join yourself if you want to be able to submit your own food and drink calorie profiles.

Another major benefit of MyFitnessPal is that they have an app that you can download to your tablet or smartphone. This makes it much easier to make quick decisions when you’re making menu decisions at a restaurant or are unsure of the healthiest place to buy a particular food.

Moving onto our joint favourite site for discovering the nutritional composition of food, which is CalorieKing.

How to use CalorieKing:

While the MyFitnessPal website is fairly self explanatory when, CalorieKing actually has a number of different options you can take advantage of.

You don’t simply have the option to enter a search term, and are instead presented with a list of food categories and popular brands you can use to narrow down your selection first.

The only improvement we would like to see made to CalorieKing (but we didn’t find this on any other site either), is the ability to filter foods based on specific requirements.

While both of the websites we just mentioned have large databases of food and drink items, neither of them allows you to search based on a specific calorie range.

For example, you might want to see a list of dessert ideas that had 20g of protein per serving and less than 300 calories. This certainly seems possible based on the information they have available.

We’re also aware that MyFitnessPal has a calculator for determining how many calories you burn as a result of performing a particular exercise for a certain amount of time.

Although this does take your weight into account for its calculations, we didn’t find it as easy to use as the recommendation we included above.

8. Running route distance calculator

There are many reasons why you would want to calculate the distance of your run.

You could have just travelled to a new city and want to match your training routine with the one you follow at home, want to add a couple of extra miles, or might simply be looking to change your route to something more interesting.

Using this distance data, you can then calculate how many calories you burned during that run, by also taking into account your speed and bodyweight.

But the difficult part can be finding a reliable way to create a running route.

Although Google Maps is available, it’s really only useful for finding the distance between two points. It would be much better if there was a tool that let you store these workouts, share them with other people, and even search other peoples workouts based around a particular location.

Unfortunately most sites offer a very poor integration of Google Maps, with perhaps a few basic features like adding in your return route.

However, there is one site that we’ve found to be an excellent distance calculator, with a wide range of other features that can be useful for analysing your performance.

Our favourite run route distance calculator:

MapMyRun is a website and app that allows you choose from a wide variety of running routes in your location, filter them down to your desired distance, then view the route complete with both distance and elevation.

You can even view the best time for the person who created that route, and send the details to your phone for you to follow when you’re actually out running.

Of course, you can also create your own running routes using the MapMyRun ‘Create Route’ tool, which has a range of useful features itself.

Whereas some route planners rely on you manually drawing a route over the roads and paths you want to take, this actually lets you choose a start and end point, then automatically creates the quickest route.

You can then make any adjustments you need to make until the route reaches your target distance.

Beyond route planning, you can also do everything from logging your food and workouts, to creating a fitness goal.

Currently these goals are based purely on distance or workout frequency, but there are plans to extend this to create weight loss goals and targets for the number of calories burned.

MapMyRun works on a freemium model, whereby you can get the basic distance calculation and route planning features for free, but you need to purchase a paid membership for access to interval training, heart rate analysis, training plans, and a whole host of additional features.

This also removes any advertisements from the site when you login.

Memberships are currently available for $5.99 per month, or $29.99 per year.

9. Sleep cycle calculator

With all of the focus we put on workout performance, goal tracking, and dieting, it’s easy to forget the importance of a good night’s rest.

There’s also a lot less written about sleep patterns than there is cardio workouts or dumbbell exercises, which can make it difficult to know what it is you should be monitoring.

However, there are now a number of companies that have integrated sleep pattern monitoring into their personal fitness trackers, as a form of wearable technology.

This will then monitor your sleep patterns and produce an easy-to-read analysis chart, which can then be used as a comparison against historical trends.

But how much sleep do we really need, and is there a ‘best time’ to fall asleep and wake up?

It all depends on how long it typically takes you to fall asleep (which is one of the things you can learn from sleep data via the personal fitness tracker), and how long each of your sleep cycles lasts.

Our favourite sleep cycle calculator:

SleepTiming is based around a hard set value of 7.5 hours sleep, which is exactly in the middle of the daily recommendation of 7 to 8 hours.

You can choose to either calculate when you need to wake up, or when you need to go to sleep by entering how many minutes it takes you to fall asleep, and the length of one of your sleep cycles.

If you’re not sure how long your sleep cycle is, 90 minutes is chosen as the default.

You will then be shown the exact time you need to sleep or wake up based on 7.5 hours of sleep, as well as 3 other times that are close to this.

Each of these 3 times is a multiple of your sleep cycle duration in minutes, ensuring that you don’t wake up mid-cycle.

But why is 90 minutes chosen as the default sleep cycle duration and not 100?

We know that this figure fits nicely into our 7.5 hours of sleep guideline with 5 cycles (5 x 90 = 450 minutes, or 7.5 hours), but what evidence is there that 90 minutes is the full duration of a cycle?

The earliest record relating to this concept is a study by W.Dement and N.Kleitman from the Department of Physiology at the University of Chicago in 1957, who observed REM sleep in adults recurring at about 90 minute intervals.

However, a more recent research paper into ‘Systematic Trends Across the Night in Human Sleep Cycles’ suggests that these sleep cycles are not perfect 90-minute periods, with around 70% of subjects in the study having sleep cycles that were up to 20 minutes either side of this mark.

If possible, 90 minutes should be used as a guideline. See how you feel after a few weeks of basing your sleep on 90 minute cycles, then change to 80 minute cycles for the 3 weeks that follow.

Finally, switch to 100 minutes for an additional 3 weeks and see which cycle length suits your body the best. Personal fitness trackers like FitBit that can track and display sleep data can also be a huge help.

10. Calculating your maximum heart rate

In a similar way to the feedback for the number of calories burned, many pieces of modern fitness equipment provide feedback on your current heart rate.

This has become a fairly standard feature amongst most mid to high level ellipticals, exercise bikes, and treadmills, with heart rate hand sensors the most common method of measurement.

But while hand sensors built into the handles is the most common form of measurement we’ve seen, you can also have in-ear transmitters, heart rate chest straps, and heart rate watches that have each been used for transmitting your heart rate to the receiver in the console of modern fitness equipment.

Why do we want to know our maximum heart rate?

Many people believe that exercise while maintaining certain percentages of your maximum heart rate can lead to different results.

For example, 70% is recognised as the ideal fat burn range, while 90% is better suited to the high intensity phases of interval training to help increase aerobic capacity and endurance.

However, also like calories burned, accurate feedback requires you to enter a basic piece of personal information. Your age.

What’s the formula?

While there are 7 different equations (including gender specific), each of them is based around your age.

Although many people – including the American Heart Association – still subscribe to the simple calculation of ‘220 – Age’, this isn’t always accurate.

Due to its simplicity, this particular calculation is incredibly easy to remember. However, this is probably one of its only benefits, as it will always underestimate your maximum heart rate.

In fact, the most recent revision to this was gender specific, and based on research conducted in 2010 at Northwestern University. According to Martha Gulati, et al., the correct maximum heart rate calculation for women is ‘206 – (0.88 x Age)’.

But if you’re looking for a formula that can truly be backed up by a larger study on both men and women between a large age range, it’s worth taking a look at The HUNT fitness study, by U. Wisloff.

This study looked at a sample size of 3320 healthy men and women aged between 18 and 89, splitting them into 10-year age groups.

They also looked to see if the formula differed based on gender, physical activity, VO2 max level, or BMI groups.

The results showed no difference between these groups, with a final agreed upon formula of 211 – 0.64 x Age. However, they also concluded that a standard error of 10.8 beats per minute must also be taken into account.

Our favourite heart rate calculator:

Based on the evidence seen in the study we just mentioned, we have to recommend Dr. Wisloff’s own calculator. This uses the same formula that was found to be so effective in the study, as well as the option to take beta blockers into account.

Bonus: 11. Weight loss equivalent chart

Although this isn’t really a calculator, we decided to include it as a way to help visualize the amount of weight you might want to lose or gain.

When we see that we’ve lost or gained 5 lbs, it can be easy to underestimate how much that actually equates to, aside from being a number on the scales.

Our table probably goes a little higher than it needs to, but you never know when you might need to know the weight of a fully grown Sumatran tiger.

Weight (lbs)	Equivelant
1	a Guinea Pig
1.5	34 Sushis
2	6 Guadelopean bananas, or a Malayan Flying Fox
3	An average human brain, or 27211 drops of water
4	3 iPads
5	a Chihuahua, 23 Blueberry muffins, or a two-liter bottle of soda
6	a human’s skin, or 34886 bees
7.5	an average newborn, or 20 iPhone 6′s
8	a human head
10	an adult Maltese Dog, a baby polar bear on the moon, or a six-foot aluminum step ladder
11	an average house cat
12	a Bald Eagle
15	10 dozen large eggs, or 2,000 paint balls
16	a sperm whale’s brain
20	a car tire
23	amount of pizza an average American eats in a year
24	a 3-gallon tub of super premium ice cream
25	an average 2 year old
30	amount of cheese an average American eats in a year
33	15 litres of water
36	a mid-size microwave
40	a 5-gallon bottle of water, or an average human leg
44	an elephant’s heart
50	a small bale of hay
55	a 5000 BTU air conditioner
60	2480 Oreos, or a fully grown male Siberian Husky, or 2 large Guinea baboons
66	fats and oils an average American eats in a year
70	an Irish Setter
77	3 Gold bars
80	the World’s Largest Ball of Tape, or a large bag of concrete
90	a newborn calf
100	a 2 month old horse, or an AGM-114 Hellfire Missile
111	red meat an average American eats in a year
117	an average fashion model (and she’s 5’11″)
118	the complete Encyclopedia Britannica
120	amount of trash you throw away in a month
130	a newborn giraffe
138	potatoes an average American eats in a year
140	refined sugar an average American eats in a year
144	an average adult woman (and she’s 5’4″)
150	the complete Oxford English Dictionary
187	an average adult man
200	2 Bloodhounds
250	an adult Giant Panda
300	a large Sumatran Tiger
400	a Welsh pony, or an adult bottlenose dolphin
600	average weight for inland male Grizzly Bear
650	largest ever Mekong giant catfish

Conclusion

These are 10 calculators that we use ourselves on a regular basis, with each one being chosen due to its ability to solve a different calculation.

But they also all have something in common – their ability to help you improve and maintain a fitter, stronger body when used as part of your daily health and fitness routine.

Are there any that you feel we’re missing out on? We’re always looking out for new fitness calculators that can be used to improve our efficiency and progress towards our goals, so please let us know in the comments below.